1. Field of the Invention
The present invention relates to a motor-equipped orthogonal gear device which can be mounted to a mating machine in various ways, which is lightweight, compact and highly efficient and which is ideal for uses in physical distribution equipment, especially in chain conveyors.
2. Description of the Prior Art
In recent years, in the physical distribution equipment market, especially in the chain conveyor market, there has been increased need for "motor-equipped orthogonal gear devices". The "motor-equipped orthogonal gear device" has a motor, and the motor shaft and output shaft of device are orthogonal.
The reason why "motor-equipped" is demanded is as follows. For example, in a physical distribution system comprising a plurality of chain conveyors, it is efficient for portions of the system to be operated only when it is necessary for these portions to operate. In this case, it is convenient that each individual chain conveyor is driven independently. Also, a disposition of individual chain conveyors is often changed in order to change the conveying path. In this case, too, it is convenient that each individual chain conveyor is driven independently.
On the other hand, the reason why "orthogonal gear device" is demanded is as follows. The largest size (the size of longitudinal direction) of motor-equipped gear devices is in axial direction of the motor. In order to improve the spatial efficiency, it is the best arrangement that the direction of the largest size (the direction of the motor shaft) is parallel to the chain conveyor. However, in order to drive the shaft of the chain conveyor, the axis of the output shaft of the gear device must be parallel to the axis of the shaft of the chain conveyor. Accordingly, the output shaft axis of the gear device and the motor shaft axis must be orthogonal.
By the way, a motor-equipped orthogonal gear device is nothing but one of the component of the mating machine (a chain conveyor and the like). Furthermore, the mating machine is also nothing but one of the component of the overall physical distribution system. Accordingly, in relation with the overall physical distribution system, it often happens that various members, which are obstructive to the installation, exist around the mating machine on which the gear device is to be mounted. It also often happens that it is not possible to leave an installed motor in use just as it is, in the case when, for example, a mating machine must be newly added in the vicinity of the motor.
In such cases, the gear device must be rotated by 180.degree. to install it, or a gear device whose shaft is extended in the opposite direction must be used.
Japanese Published Application 2-53656 discloses a method for providing two types of flange series (product variations) so as to facilitate such work.
Also, Japanese Laid-Open Utility Model Application 2-22450 discloses a technique in which a gearbox directly coupled with a motor is in the shape of a hexahedron, and holes for mounting are present on faces of the gearbox that do not directly face the motor.
However, with the above-described publicly known conventional methods, there are the following difficulties that still have to be overcome.
The method disclosed by Japanese Published Application 2-53656 involves the problem that gear devices of two types of flange series (product variations) have to be designed and provided in order to allow a 4-direction (0.degree., 90.degree., 180.degree., 270.degree.) rotatable mounting. Furthermore, when a gear device has to rotate in relation with the disposition of a mating machine, there is the problem that it is not always possible to freely rotate the gear device itself. That is, in order to secure four mounting directions, two types of product variations are always necessary, and there is a disadvantage that a change in the position of the holes for mounting against the output shaft occurs, if the identical device is merely rotated.
Furthermore, the following problem is associated with the method disclosed by Japanese Laid-Open Utility Model Application 2-22450.
FIG. 1 shows an example of a motor-equipped gear device which relates to an embodiment of the present invention described in detail hereinafter and which is used in a mating machine (chain conveyor) that is part of a physical distribution system. As shown in this example, in chain conveyors for example, the length Sa, Sb from the center Os of the output shaft 62 to the outer circumference of the gearbox 64 must be smaller than the turning radius Rc of the chain conveyor C in order to avoid interference with an object W being conveyed on the chain conveyor C. The center Os of the output shaft 62 in such gear devices is therefore often displaced (offset) from the center Ob of the holes for the mounting.
If the technique disclosed by Japanese Laid-Open Utility Model Application 2-22450 is applied in this case, then the spirit of the disclosure demands that the holes for mounting shall be provided at the vertex positions of a square being arranged "coaxial" to the output shaft. The arrangement of the holes for mounting must therefore be such that the pitch thereof is relatively smaller when it is compared with the overall size of the gearbox. Accordingly, the capability of the mounting bolts accommodating the reactive force of the torque of the drive shaft tends to become small considering the size of the gearbox.
As in the example of Japanese Laid-Open Utility Model Application 2-22450, in devices using a worm reduction gear, the efficiency of the worm reduction gear itself is low and the transmission torque is small considering the size of the gearbox. Therefore, even such a bolt arrangement is certainly adequate.
However, when a high-efficiency and large-torque reduction gear is required as in conveyor applications, the mounting force by the bolts must provide a large securing strength. Therefore, the method of Japanese Laid-Open Utility Model Application 2-22450 is not practical, because it does not allow the holes for mounting to be arranged near the outer circumference of the gearbox.